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Message-Id: <20250322-fixed-type-genmasks-v7-0-da380ff1c5b9@wanadoo.fr>
Date: Sat, 22 Mar 2025 18:23:11 +0900
From: Vincent Mailhol via B4 Relay <devnull+mailhol.vincent.wanadoo.fr@...nel.org>
To: Yury Norov <yury.norov@...il.com>,
Lucas De Marchi <lucas.demarchi@...el.com>,
Rasmus Villemoes <linux@...musvillemoes.dk>,
Jani Nikula <jani.nikula@...ux.intel.com>,
Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
Rodrigo Vivi <rodrigo.vivi@...el.com>,
Tvrtko Ursulin <tursulin@...ulin.net>, David Airlie <airlied@...il.com>,
Simona Vetter <simona@...ll.ch>, Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, intel-gfx@...ts.freedesktop.org,
dri-devel@...ts.freedesktop.org, Andi Shyti <andi.shyti@...ux.intel.com>,
David Laight <David.Laight@...LAB.COM>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Jani Nikula <jani.nikula@...el.com>,
Vincent Mailhol <mailhol.vincent@...adoo.fr>
Subject: [PATCH v7 0/5] bits: Fixed-type GENMASK_U*() and BIT_U*()
Introduce some fixed width variant of the GENMASK() and the BIT()
macros in bits.h. Note that the main goal is not to get the correct
type, but rather to enforce more checks at compile time. For example:
GENMASK_U16(16, 0)
will raise a build bug.
This series is a continuation of:
https://lore.kernel.org/intel-xe/20240208074521.577076-1-lucas.demarchi@intel.com
from Lucas De Marchi. Above series is one year old. I really think
that this was a good idea and I do not want this series to die. So I
am volunteering to revive it.
Meanwhile, many changes occurred in bits.h. The most significant
change is that __GENMASK() was moved to the uapi headers. For this
reason, a new GENMASK_TYPE() is introduced instead and the uapi
__GENMASK() is left untouched.
Finally, I do not think it makes sense to expose the fixed width
variants to the asm. The fixed width integers type are a C concept. So
the GENMASK_U*() are only visible to the non-asm code. For asm, the
long and long long variants seems sufficient.
This series does not modify the actual GENMASK(), GENMASK_ULL() and
GENMASK_U128(). A consolidation of the existing genmasks will be
proposed later on in a separate series.
As requested, here are the bloat-o-meter stats:
$ ./scripts/bloat-o-meter vmlinux_before.o vmlinux_after.o
add/remove: 0/0 grow/shrink: 0/0 up/down: 0/0 (0)
Function old new delta
Total: Before=22723481, After=22723481, chg +0.00%
(done with GCC 12.4.1 on an x86_64 defconfig)
--
2.43.0
---
Changes from v6:
- Split the series in two: this series leave any existing GENMASK*()
unmodified. The consolidation will be done in a separate series.
- Collect some Reviewed-by tag.
- Address miscellaneous nitpick on the code comments and the line
wrapping (details in each patch).
- Link to v6: https://lore.kernel.org/r/20250308-fixed-type-genmasks-v6-0-f59315e73c29@wanadoo.fr
Changes from v5:
- Update the cover letter message. I was still refering to
GENMASK_t() instead of GENMASK_TYPE().
- Add a comment in the cover letter to explain that a common
GENMASK_TYPE() for C and asm wouldn't allow to generate the u128
variant.
- Restore the comment saying that BUILD_BUG_ON() is not available in
asm code.
- Add a FIXME message to highlight the absence of the asm GENMASK*()
unit tests.
- Use git's histogram diff algorithm
- Link to v5: https://lore.kernel.org/r/20250306-fixed-type-genmasks-v5-0-b443e9dcba63@wanadoo.fr
Changes from v4:
- Rebase on https://github.com/norov/linux/tree/bitmap-for-next
- Rename GENMASK_t() to GENMASK_TYPE()
- First patch of v4 (the typo fix 'init128' -> 'int128') is removed
because it was resent separately in:
https://lore.kernel.org/all/20250305-fix_init128_typo-v1-1-cbe5b8e54e7d@wanadoo.fr
- Replace the (t)~ULL(0) by type_max(t). This way, GENMASK_TYPE()
can now be used to generate GENMASK_U128().
- Get rid of the unsigned int cast for the U8 and U16 variants.
- Add the BIT_TYPE() helper macro.
- Link to v4: https://lore.kernel.org/r/20250305-fixed-type-genmasks-v4-0-1873dcdf6723@wanadoo.fr
Changes from v3:
- Rebase on v6.14-rc5
- Fix a typo in GENMASK_U128() comment.
- Split the asm and non-asm definition of
- Replace ~0ULL by ~ULL(0)
- Since v3, __GENMASK() was moved to the uapi and people started
using directly. Introduce GENMASK_t() instead.
- Link to v3: https://lore.kernel.org/intel-xe/20240208074521.577076-1-lucas.demarchi@intel.com
Changes from v2:
- Document both in commit message and code about the strict type
checking and give examples how it´d break with invalid params.
- Link to v2: https://lore.kernel.org/intel-xe/20240124050205.3646390-1-lucas.demarchi@intel.com
Link to v1: https://lore.kernel.org/intel-xe/20230509051403.2748545-1-lucas.demarchi@intel.com
---
Lucas De Marchi (3):
bits: introduce fixed-type BIT_U*()
drm/i915: Convert REG_GENMASK*() to fixed-width GENMASK_U*()
test_bits: add tests for GENMASK_U*()
Vincent Mailhol (2):
bits: introduce fixed-type GENMASK_U*()
test_bits: add tests for BIT_U*()
drivers/gpu/drm/i915/i915_reg_defs.h | 108 ++++-------------------------------
include/linux/bitops.h | 1 -
include/linux/bits.h | 57 +++++++++++++++++-
lib/test_bits.c | 30 ++++++++++
4 files changed, 96 insertions(+), 100 deletions(-)
---
base-commit: e3f42c436d7e0cb432935fe3ae275dd8d9b60f71
change-id: 20250228-fixed-type-genmasks-8d1a555f34e8
Best regards,
--
Vincent Mailhol <mailhol.vincent@...adoo.fr>
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